Photomasks are high precision plates containing microscopic images of electronic circuits. Photomasks are typically made from very flat pieces of quartz or glass with a layer of chrome on one side. Etched in the chrome is a portion of an electronic circuit design. This circuit design on the mask is also called geometry.
A typical photomask used in the production of semiconductor devices is formed from a “blank” or “undeveloped” photomask. As shown in FIG. 1, a typical blank photomask 10 is comprised of three or four layers. The first layer 11 is a layer of quartz or other substantially transparent material, commonly referred to as the substrate. The next layer is typically a layer of opaque material 12, such as Cr, which often includes a third layer of antireflective material 13, such as CrO. The antireflective layer, may or may not be included in any given photomask. The top layer is typically a layer of photosensitive resist material 14. Other types of photomasks are also known and used including, but not limited to, phase shift masks, embedded attenuated or alternating aperture phase shift masks.
The desired pattern of opaque material 12 to be created on the photomask 10 may be defined by an electronic data file loaded into an exposure system which typically scans an electron beam (E-beam) or laser beam in a raster or vector fashion across the blank photomask. One such example of a raster scan exposure system is described in U.S. Pat. No. 3,900,737 to Collier. Each unique exposure system has its own software and format for processing data to instruct the equipment in exposing the blank photomask. As the E-beam or laser beam is scanned across the blank photomask 10, the exposure system directs the E-beam or laser beam at addressable locations on the photomask as defined by the electronic data file. The areas of the photosensitive resist material that are exposed to the E-beam or laser beam become soluble while the unexposed portions remain insoluble.
In order to determine where the e-beam or laser should expose the photoresist 14 on the blank photomask 10, and where it should not, appropriate instructions to the processing equipment need to be provided, in the form of a jobdeck. In order to create the jobdeck the images of the desired pattern are broken up (or fractured) into smaller standardized shapes, e.g., rectangles and trapezoids. The fracturing process can be very time consuming. After being fractured, the image may need to be further modified by, for example, sizing the data if needed, rotating the data if needed, adding fiducial and internal reference marks, etc. Typically a dedicated computer system is used to perform the fracturing and/or create the jobdecks. The jobdeck data must then be transferred to the processing tools, to provide such tools with the necessary instructions to expose the photomask.
As shown in FIG. 2, after the exposure system has scanned the desired image onto the photosensitive resist material 14, the soluble photosensitive resist material is removed by means well known in the art, and the unexposed, insoluble photosensitive resist material 14′ remains adhered to the opaque material 13 and 12. Thus, the pattern to be formed on the photomask 10 is formed by the remaining photosensitive resist material 14′.
The pattern is then transferred from the remaining photoresist material 14′ to the photomask 10 via known etch processes to remove the antireflective material 13 and opaque materials 12 in regions which are not covered by the remaining photoresist 14′. There are a wide variety of etching processes known in the art, including dry etching as well as wet etching, and thus a wide variety of equipment used to perform such etching. After etching is complete, the remaining photoresist material 14′ is stripped or removed and the photomask is completed, as shown in FIG. 3. In the completed photomask, the pattern as previously reflected by the remaining antireflective material 13′ and opaque materials 12′ are located in regions where the remaining photoresist 14′ remain after the soluble materials were removed in prior steps.
In order to determine if there are any unacceptable defects in a particular photomask, it is necessary to inspect the photomasks. A defect is any flaw affecting the geometry. This includes chrome where it should not be (chrome spots, chrome extensions, chrome bridging between geometry) or unwanted clear areas (pin holes, clear extensions, clear breaks). A defect can cause the customer's circuit not to function. The customer will indicate in its defect specification the size of defects that will affect their process. All defects that size and larger must be repaired, or if they can not be repaired the mask must be rejected and rewritten.
Typically, automated mask inspection systems, such as those manufactured by KLA Instruments Corporation or ETEC, an Applied Materials company, are used to detect defects. Such automated systems direct an illumination beam at the photomask and detect the intensity of the portion of the light beam transmitted through and reflected back from the photomask. The detected light intensity is then compared with expected light intensity, and any deviation is noted as a defect. The details of one system, can be found in U.S. Pat. No. 5,563,702 assigned to KLA Instruments Corporation.
After passing inspection, a completed photomask is cleaned of contaminants. Next, a pellicle may be applied to the completed photomask to protect its critical pattern region from airborne contamination. Subsequent through pellicle defect inspection may be performed. Sometimes either before or after a pellicle is applied, the photomask may be cut. After these steps are completed, the completed photomask is sent to a customer for use to manufacture semiconductor and other products. In particular, photomasks are commonly used in the semiconductor industry to transfer micro-scale images defining a semiconductor circuit onto a silicon or gallium arsenide substrate or wafer. The process for transferring an image from a photomask to a silicon substrate or wafer is commonly referred to as lithography or microlithography.
Typically, as shown in FIG. 4, the semiconductor manufacturing process comprises the steps of deposition, photolithography, and etching. During deposition, a layer of either electrically insulating or electrically conductive material (like a metal, polysilicon or oxide) is deposited on the surface of a silicon wafer. This material is then coated with a photosensitive resist. The photomask is then used much the same way a photographic negative is used to make a photograph. Photolithography involves projecting the image on the photomask onto the wafer. If the image on the photomask is projected several times side by side onto the wafer, this is known as stepping and the photomask is called a reticle.
As shown in FIG. 5, to create an image 21 on a semiconductor wafer 20, a photomask 10 is interposed between the semiconductor wafer 20, which includes a layer of photosensitive material, and an optical system 22. Energy generated by an energy source 23, commonly referred to as a Stepper, is inhibited from passing through the areas of the photomask 10 where the opaque material are present. Energy from the Stepper 23 passes through the transparent portions of the quartz substrate 11 not covered by the opaque material 12 and the antireflective material 13. The optical system 22 projects a scaled image 24 of the pattern of the opaque material 12 and 13 onto the semiconductor wafer 20 and causes a reaction in the photosensitive material on the semiconductor wafer. The solubility of the photosensistive material is changed in areas exposed to the energy. In the case of a positive photolithographic process, the exposed photosensistive material becomes soluble and can be removed. In the case of a negative photolithographic process, the exposed photosensistive material becomes insoluble and unexposed soluble photosensistive material is removed.
After the soluble photosensistive material is removed, the image or pattern formed in the insoluble photosensistive material is transferred to the substrate by a process well known in the art which is commonly referred to as etching. Once the pattern is etched onto the substrate material, the remaining resist is removed resulting in a finished product. A new layer of material and resist is then deposited on the wafer and the image on the next photomask is projected onto it. Again the wafer is developed and etched. This process is repeated until the circuit is complete. Because, in a typical semiconductor device many layers may be deposited, many different photomasks may be necessary for the manufacture of even a single semiconductor device. Indeed, if more than one piece of equipment is used by a semiconductor manufacturer to manufacturer a semiconductor device, it is possible more than one photomask may be needed, even for each layer. Furthermore, because different types of equipment may also be used to expose the photoresist in the different production lines, even the multiple identical photomask patterns may require additional variations in sizing, orientation, scaling and other attributes to account for differences in the semiconductor manufacturing equipment. Similar adjustments may also be necessary to account for differences in the photomask manufacturer's lithography equipment. These differences need to be accounted for in the photomask manufacturing process. Heretofore, the only way known to account for such differences involved manual intervention by an operator to change the data being provided to processing equipment.
A critical aspect in the manufacture of a photomasks is to reduce the time it takes from receiving an order to providing a customer with a photomask. In a typical photomask production, a lot of steps are necessary to perform the tasks necessary to form a completed photomask.
First, the order must be taken, and the customers information regarding the photomask to be manufactured and billing or other processing information must be taken. In the past, this information has been provided either manually in hard copy, or electronically in the form of a floppy disk, magnetic tape, cassette tape or by modem.
Once the photomask manufacturer receives the necessary information, operators are then required to sort through the information received and manually forward to the appropriate processing station or department the information provided. For example, the billing information would have to be forwarded to the billing department, and pattern data necessary to perform the fracturing needs to be provided to the fracturing computer, and the remaining jobdeck information would have to be forwarded to the appropriate processing station. If information is provided in a different format than the manufacturers computer provides, this fact would also need to be identified manually, and then the file converted to an appropriate format. If the photomask manufacturer desired to track the progress of the photomask in production, it was necessary to individually contact each station and ascertain the status from the operator. To the extent that the semiconductor manufacturer needs the same pattern to be used by multiple different machines, an operator is required to manually program the fracturing computer to make appropriate modifications. Similarly, to the extent certain customer's specified format needs to be modified due to photomask manufacturing processes being used, these types of modifications of data input to the fracturing computer also heretofore needed to be entered manually by an operator. The system disclose provides no expressed way to account and handle these variations.
A long standing problem in the photomask production industry is how to reduce the time it takes from receipt of a customer order to formation and delivery of the processed photomask. Some ways used in the past to expedite this process has been the creation of industry standards, such as the SEMI P10 standard which has been modified and updated over the years, which dictate the form in which data should be electronically provided to photomask manufacturers. While such standards are helpful, they have not in and of themselves achieved a seamless automation of the processing of information necessary in the manufacture of the photomasks.
In the past, one of our predecessor organizations, AlignRite Corporation, attempted to expedite the delivery of the electronic data by use of an Internet based delivery system. However, although the AlignRite System was capable of rapid delivery of the photomask data from the customer to the computer system of the photomask manufacturer and was capable of validating the accuracy of this data in real time, this prior system did not provide for a fully automated process upon receipt of the information. Operators were still necessary to identify and process the electronic data upon receipt. Standard modifications to the data that may be customer dependent or facility dependent would also have to entered manually by operators. Each time a manual change would have to be entered the risk of human error increased, and the overall length of the job would be extended.
Others have disclosed systems in which manufacturing and billing data are down-loaded over the Internet and verified on-line automatically. This system is described in PCT Publication Number 02/03141, published on Jan. 10, 2002 to DuPont Photomask, Inc. After requiring the data provided to be in a specified uniform format, this system generally describes that the data is electronically processed. While this system discloses the use of the data electronically received and on-line verified to be used in billing systems and for fracturing systems, this system does not provide for automatic transfer of data between these systems and other systems. This system also does not provide any flexibility for the acceptance of varying forms of data, as the verification process disclosed requires a specified uniform format. Further, this system also does not account for other order variables that need to be modified in the jobdeck and thus are likely to require human intervention. This system also fails to provide an automated and interactive monitoring system which will provide for prompt identification and notification of status and errors, while optionally allowing an operator to manually intervene and correct such errors.
It is another object of the present invention to eliminate manual intervention in the transmission and processing of customer data for manufacture of a photomask.
It is another object of the present invention to reduce the lead time and total processing time it takes from the time that a photomask manufacturer receives the necessary processing information from a customer to the time it takes to deliver the finished photomask to that customer.
It is another object of the present invention to improve the accuracy and efficiency in which customer photomask data is processed and transmitted for manufacture.
It is another object of the present invention to solve the shortcomings of the prior art.
Other objects will become apparent from the foregoing description.